import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		long F0 = scan.nextInt();
		long F1 = scan.nextInt();
		long N = scan.nextLong();
		scan.close();
		long ans = 0;
		if(N % 3 == 0) {
			ans = F0;
		}else if(N % 3 == 1) {
			ans = F1;
		}else {
			ans = F0 ^ F1;
		}
		System.out.println(ans);
	}
}